1. Field of the Invention
This invention relates to a system and method for imaging the contents of containers. The invention more particularly concerns the imaging and detection of certain items which are hidden from view contained within the containers. The containers to which the invention relates will generally be mounted to a lorry or other vehicle, but they may also be standalone containers that are being carried on some other vehicle or moving platform, such as a train. The invention is particularly aimed at the detection of smuggled contraband through ports and across borders.
2. Discussion of Prior Art
The smuggling of contraband across borders has been going on for a great many years and much effort is put in by government bodies in an attempt to eradicate the problem. As fast as ways of countering the smuggling are found, the smugglers are adapting their methods to avoid capture. Ports are also becoming more busy as inter state trade increases, which exacerbates the problem. Items such as cigarettes and alcoholic drinks are often targeted by the smugglers in an attempt to avoid the duty payable on such items. More recently, there has been a growth in the smuggling of illegal immigrants across borders.
Methods of detecting such contraband do exist. Sniffer dogs can be used to great effect in an open truck to find humans, and manual searching can be used to find alcoholic drinks and cigarettes. Either method is very time consuming as a truck needs to be opened to be searched, resulting in either long delays whilst all trucks are searched, or running a great risk of missing some contraband by only selecting certain trucks for searching.
Another method used to find human cargo is to push a CO2 sensor into the container volume and measure the quantities of the gas present. A high reading will be taken as being suspicious, and a final manual check can then be carried out. This is quicker than the previous method as not every truck is opened, but suffers from the disadvantage that it is not appropriate for all container types, as some don't have an opening suitable for insertion of the sensor. Again, the truck must be stationary for this to happen. The method is also of no use against cigarettes or alcohol.
Another method that has been recently used is to image the container using a large X-ray machine. This can provide a relatively clear picture of the contents of the container, but does suffer from some disadvantages. Firstly, current systems take a few minutes to produce a final image of the contents, leading to the delays discussed above. Secondly, the scanning process is also relatively slow, and the lorry must be stationary whilst the scanning is carried out. Thirdly, by the very nature of X-rays, there is some perceived danger in being excessively exposed to them, so they are not suitable for the detection of human cargo.